Novel vlps derived from cells that do not express a viral matrix or core protein

ABSTRACT

The present invention discloses novel influenza virus-like particles (VLPs) that contain chimeric proteins or influenza membrane proteins. The chimeric proteins are derived from fragments of influenza membrane proteins fused to heterologous proteins. The invention includes antigenic formulations and vaccines comprising VLPs of the invention as well as methods of making and administering VLPs to vertebrates, including methods of inducing immunity to infections, such as influenza.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. provisional application60/940,201, filed May 25, 2007, which is herein incorporated byreference in its entirety.

BACKGROUND

Influenza virus is a member of the Orthomyxoviridae family, and can befurther classified into three subtypes: A, B, and C (for review, seeMurphy and Webster, (1996) Virology, Vol. 1, pp. 1397-1444.Lippincott-Raven, Philadelphia). Influenza subtype A causes the mostsevere disease in humans. The A strain can be subdivided into differentserotypes according to which forms of two surface antigens(hemagglutinin and neuraminidase) are expressed. The influenza virus isan enveloped, segmented, negative strand RNA virus, which encodesseveral viral proteins. The mature influenza virion containshemagglutinin (HA), neuraminidase (NA), matrix (M1), proton ion-channelprotein (M2), nucleoprotein (NP), polymerase basic protein 1 (PB1),polymerase basic protein 2 (PB2), polymerase acidic protein (PA), andnonstructural protein 2 (NS2) proteins. The HA, NA, M1, and M2 aremembrane associated, whereas NP, PB1, PB2, PA, and NS2 are nucleocapsidassociated proteins. The NS1 is the only nonstructural protein notassociated with virion particles but specific for influenza-infectedcells. The M1 protein is the most abundant protein in influenzaparticles. The HA and NA proteins are envelope glycoproteins,responsible for virus attachment and penetration of the viral particlesinto the cell, and the sources of the major immunodominant epitopes forvirus neutralization and protective immunity. Both HA and NA proteinsare considered the most important components for prophylactic influenzavaccines.

Influenza virus infection is initiated by the attachment of the virionsurface HA protein to a sialic acid-containing cellular receptor(glycoproteins and glycolipids). The NA protein mediates processing ofthe sialic acid receptor, and virus penetration into the cell occursthrough a receptor-mediated endocytosis, which is dependent on the viralHA protein. Within the acidic endosomes, the HA proteins of internalizedinfluenza virions undergo conformational changes that lead to fusion ofviral and host cell membranes followed by virus uncoating, andM2-mediated release of M1 proteins from nucleocapsid-associatedribonucleoproteins (RNPs). The RNPs then migrate into the cell nucleusfor viral RNA synthesis. Antibodies to HA molecules can prevent virusinfection by neutralizing virus infectivity, whereas antibodies to NAproteins mediate their effect on the early steps of viral replication.

Inactivated influenza A and B virus vaccines are currently sold astrivalent vaccines for parenteral administration. These trivalentvaccines are produced as monovalent bulk in the allantoic cavity ofembryonated chick eggs, purified by rate zonal centrifugation or columnchromatography, inactivated with formalin or β-propiolactone, andformulated as a blend of the type A and type B strains of influenzaviruses in circulation among the human population for a given year. Theavailable commercial influenza vaccines are whole virus (WV) orsubvirion (SV; split or purified surface antigen) virus vaccines. The WVvaccine contains intact, inactivated virions. SV vaccines treated withsolvents such as tri-n-butyl phosphate (Flu-Shield, Wyeth-Lederle)contain nearly all of the viral structural proteins and some of theviral envelope proteins. SV vaccines solubilized with Triton X-100(Fluzone, Sanofi-Aventis; Fluvirin, Novartis) contain aggregates of HAmonomers, NA, and NP principally, although residual amounts of otherviral structural proteins are present. A live attenuated cold-adaptedvirus vaccine (FluMist, MedImmune) was granted marketing approval by theFDA for commercial usage as an intranasally delivered vaccine indicatedfor active immunization and the prevention of disease caused byinfluenza A and B viruses in healthy children and adolescents (5-17years of age) and healthy adults (18-49 years of age).

Several recombinant products have been developed as recombinantinfluenza vaccine candidates. These approaches have focused on theexpression, production, and purification of influenza virus type A HAand NA proteins, including expression of these proteins usingbaculovirus infected insect cells (Crawford et al, 1999; Johansson,1999; Treanor et al., 1996), viral vectors (Pushko et al. (1997),Virology, 239, 389-401; Berglund et al. (1999), Vaccine, 17, 497-507),and DNA vaccine constructs (Olsen et al. (1997), Vaccine, 15,1149-1156).

Crawford et al. (1999), Vaccine, 17, 2265-2274 demonstrated thatinfluenza HA expressed in baculovirus infected insect cells is capableof preventing lethal influenza disease caused by avian H5 and H7influenza subtypes. At the same time, another group demonstrated thatbaculovirus-expressed influenza HA and NA proteins induce immuneresponses in animals superior to those induced by a conventional vaccine(Johansson et al., (1999) Vaccine, 17, 2073-2080). Immunogenicity andefficacy of baculovirus-expressed hemagglutinin of equine influenzavirus was compared to a homologous DNA vaccine candidate (Olsen et al.(1997), Vaccine, 15, 1149-1156). Taken together, these studiesdemonstrated that a high degree of protection against influenza viruschallenge can be induced with recombinant HA or NA proteins, usingvarious experimental approaches and in different animal models.

Lakey et al. (1996), J. Infect Dis., 174, 838-841 showed that abaculovirus-derived influenza HA vaccine was well-tolerated andimmunogenic in human volunteers in a Phase I dose escalation safetystudy. However, results from Phase II studies conducted at severalclinical sites in human volunteers vaccinated with several doses ofinfluenza vaccines comprised of HA and/or NA proteins indicated that therecombinant subunit protein vaccines did not elicit protective immunity.These results indicated that conformational epitopes displayed on thesurface of HA and NA peplomers of infectious virions were important inthe elicitation of neutralizing antibodies and protective immunity.

Regarding the inclusion of other influenza proteins in recombinantinfluenza vaccine candidates, a number of studies have been carried out,including the experiments involving influenza nucleoprotein, NP, aloneor in combination with M1 protein (Ulmer et al. (1993), Science 259,1745-1749; Ulmer et al. (1998), J. Virol., 72, 5648-5653; Zhou et al.(1995) Proc. Natl. Acad. Sci., 92, 3009-3013; Tsui et al. (1998), J.Virol., 72, 6907-6910). These vaccine candidates, which were composed ofquasi-invariant inner virion proteins, elicited a broad spectrumimmunity that was primarily cellular (both CD4⁺ and CD8⁺ memory Tcells). These experiments involved the use of the DNA or viral geneticvectors. Relatively large amounts of injected DNA were needed, asresults from experiments with lower doses of DNA indicated little or noprotection (Chen et al., 1998). Hence, further preclinical and clinicalresearch may be required to evaluate whether such DNA-based approachesinvolving influenza NP and M1 are safe, effective, and persistent.

Recently, in an attempt to develop more effective vaccines forinfluenza, particulate proteins were used as carriers of influenza M2protein epitopes. The rationale for development of an M2-based vaccinewas that protective immunity against influenza was elicited by M2proteins in animal studies (Slepushkin et al. (1995), Vaccine, 13,1399-1402. Neirynck et al. (1999) used a 23-aa long M2 transmembranedomain as an amino terminal fusion partner with the hepatitis B viruscore antigen (HBcAg) to expose the M2 epitope(s) on the surface of HBcAgcapsid-like particles. However, in spite of the fact that bothfull-length M2 protein and M2-HBcAg particles induced detectableantibodies and protection in mice, it was unlikely that future influenzavaccines would be based exclusively on the M2 protein, as the M2 proteinwas present at low copy number per virion, was weakly antigenic, wasunable to elicit antibodies that bound free influenza virions, and wasunable to block virus attachment to cell receptors (i.e. virusneutralization).

Since previous research has shown that the surface influenzaglycoproteins, HA and NA, are the primary targets for elicitation ofprotective immunity against influenza virus, a new vaccine candidate mayinclude these viral antigens as a protein macromolecular particle, suchas a virus-like particle (VLP). VLPs are structurally similar to maturevirions, but lack the viral genome making it impossible for viralreplication to occur. VLPs can contain antigenic proteins, such as HA,and NA, like intact virus and can be constructed to express foreignstructural proteins on their surface as well. Furthermore, the particlewith these influenza antigens may display conformational epitopes thatelicit neutralizing antibodies to multiple strains of influenza viruses.

Several studies have demonstrated that recombinant influenza proteinscould self-assemble into VLPs in cell culture using mammalian expressionplasmids or baculovirus vectors (Gomez-Puertas et al. (1999), J. Gen.Virol, 80, 1635-1645; Neumann et al. (2000), J. Virol., 74, 547-551;Latham and Galarza (2001), J. Virol., 75, 6154-6165). Gomez-Puertas etal. (1999), J. Gen. Virol., 80, 1635-1645, demonstrated that efficientformation of influenza VLPs depends on the expression levels of viralproteins. Neumann et al. (2000) established a mammalian expressionplasmid-based system for generating infectious influenza virus-likeparticles entirely from cloned cDNAs. Latham and Galarza (2001) reportedthe formation of influenza VLPs in insect cells infected withrecombinant baculovirus co-expressing HA, NA, M1, and M2 genes. Thisstudy demonstrated that influenza virion proteins self-assemble uponco-expression in eukaryotic cells and that the M1 matrix protein wasrequired for VLP production.

SUMMARY OF THE INVENTION

The present invention discloses novel VLPs generated by expressinginfluenza membrane proteins or chimeras of influenza membrane proteinswithout the co-expression of influenza M1 matrix protein in eukaryotichost cells. The chimeric proteins are made by fusing either cytoplasmicor transmembrane domains from influenza membrane proteins with antigenicproteins from other influenza subtypes or other infectious agents incells. The VLPs of the invention find use as antigenic formulations orvaccine preparations.

The present invention provides a purified VLP comprising at least onechimeric influenza membrane protein, wherein the VLP does not contain aninfluenza matrix (M1) protein. In one embodiment, said VLP furthercomprises at least one additional protein from an infectious agent. Thechimeric protein can contain the cytoplasmic tail or the transmembranedomain from an influenza membrane protein. The influenza membraneprotein may be HA, NA, or M2. In another embodiment of the invention,said VLP does not contain a viral matrix or core protein. In anotherembodiment, said VLP comprises an enzymatically active influenza NAprotein.

The present invention also provides a purified VLP comprising at leastone influenza membrane protein, wherein the VLP does not contain aninfluenza matrix (M1) protein. In one embodiment, said VLP furthercomprises at least one additional protein from an infectious agent. Inanother embodiment, said influenza membrane protein is HA. The HAprotein may be derived from a seasonal or avian HA protein. In anotherembodiment, said VLP further comprises an influenza NA protein. Inanother embodiment, said HA and NA are H5N1. In another embodiment, saidVLP does not contain a viral matrix or core protein.

The present invention also discloses methods of making VLPs comprisingexpressing at least one chimeric influenza membrane protein or influenzamembrane protein in a cell, and purifying the VLPs, wherein said celldoes not express and influenza matrix (M1) protein. In one embodiment,said method further comprises expressing at least one additional proteinfrom an infectious agent in the cell.

The present invention also provides vaccines and antigenic formulationscomprising VLPs disclosed herein, including for instance, a VLPcomprising at least one chimeric influenza membrane protein, whereinsaid VLP does not contain an influenza matrix (M1) protein. In someembodiments, vaccines and antigenic formulations comprise a VLPcomprising at least one influenza membrane protein, wherein said VLPdoes not contain an influenza matrix (M1) protein. In other embodiments,said VLP further comprises at least one additional protein from aninfectious agent. The invention also discloses methods of inducingprotective immunity to an infection in a subject comprisingadministering a vaccine or antigenic formulation disclosed herein.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic of a sucrose gradient used for the separation ofVLPs from contaminants. Fraction numbers are indicated on the left side.

FIG. 2 depicts Western blots of samples from Sf9 cells infected withrecombinant baculovirus expressing various combinations of influenzaproteins. The samples were purified using a sucrose gradient andfraction 3 (collected as shown in FIG. 1) was loaded onto the gels. Thetop blot is an analysis of samples taken two days post-infection, whilethe bottom blot is an analysis of samples taken three dayspost-infection. Blots were probed with serum against H3N₂ influenzavirus. Lane 1=molecular weight standard; lanes 2 and 3=cells infectedwith recombinant baculovirus expressing HA, NA, NP, M1 and M2; lane4=cells infected with wild-type baculovirus; lane 5=cells infected withrecombinant baculovirus expressing HA and NA; lane 6=uninfected Sf9cells; lane 7=cells infected with recombinant baculovirus expressing HPV16L1.

FIG. 3 shows the HPLC chromatographic profile for samples of influenzavirions, cells infected with baculovirus expressing HA and NA influenzaproteins, and controls.

FIG. 4 depicts the procedure for obtaining pure virus-like particles bysucrose gradient ultracentrifugation.

FIG. 5 shows a Western blot of a fractionated sample of cells expressinginfluenza HA and NA proteins. The blot was probed with serum againstH3N₂ influenza virus. Lanes 3 through 14 contain fractions 0 through 11of the sucrose gradient as shown in FIG. 4. The immunoreactive bandspresent in lanes 5-11 indicate the presence of VLPs in the sample.

FIG. 6 shows the HPLC chromatographic profile for lysates of cellsexpressing influenza HA and NA proteins, influenza VLPs, and lysates ofcells expressing control protein (HPV 16L1).

FIG. 7 depicts a Western blot of media supernatants purified through 20%sucrose cushion. The media supernatants were obtained from cellsinfected with recombinant baculovirus expressing different influenzaproteins. The blot was probed with a polyclonal antibody to influenzavirus. Lane 1=molecular weight standard; lane 2=HA+NA+NP+M1+M2; lane3=HA+NA+M1+M2; lane 4=HA; lane 5=NA; lane 6=M1; and lane 7=M2. Thepresence of immunoreactive bands indicates VLP formation.

FIG. 8 depicts the chimeric protein comprising eGFP with the cytoplasmicdomain (Cy) of influenza protein M2 (A) or influenza protein HA (B).

FIG. 9A is a coomassie-stained gel of supernatants and lysates of cellsinfected with recombinant baculovirus expressing chimeric proteins (eGFPfused to the cytoplasmic tail of either influenza M2 or influenza HAprotein). FIG. 8B shows the corresponding western blot of the geldepicted in A. The blot was probed with a polyclonal antibody againstGFP. The presence of bands in lanes 2 and 4 indicate the formation ofVLPs in cells expressing the chimeric proteins.

FIG. 10 depicts the results of SDS-PAGE and western blot analyses oflysates from cells infected with recombinant baculovirus expressing achimeric protein containing the transmembrane domain of influenza HAprotein fused to glycoprotein E of Varicella Zoster virus. Lysates weresubject to fractionation on a 20%-60% sucrose gradient and the VLPfraction (30% sucrose) was loaded on to SDS-PAGE gels. A.Coomassie-stained gel of fractionated lysates from infected cells. B.Western blot of proteins from gel depicted in part A probed forglycoprotein E of VZV. C. Western blot of proteins from gel in part Aprobed for Influenza M1 matrix protein.

DETAILED DESCRIPTION

As used herein, the term “virus-like particle” (VLP) refers to astructure that in at least one attribute resembles a virus but which hasbeen demonstrated to be non-infectious. Virus-like particles inaccordance with the invention do not carry genetic information encodingfor the proteins of the virus-like particles. In general, virus-likeparticles lack a viral genome and cannot replicate. In addition,virus-like particles can often be produced in large quantities byheterologous expression and can be easily purified.

As used herein, the term “purified VLPs” refers to a preparation of VLPsof the invention that is at least 50%, 55% 60%, 65%, 70%, 75%, 80%, 85%,90%, 95%, 96%, 97%, 98%, 99% or greater, free from other molecules(exclusive of solvent) in a mixture. For example, VLPs of the inventioncan be substantially free of other viruses, proteins, lipids, andcarbohydrates associated with making VLPs of the invention.

As used herein, the term “chimeric protein” refers to a protein thatcontains a fragment of an influenza membrane protein fused to aheterologous protein. The heterologous protein may be a protein derivedfrom another strain of influenza or a protein derived from anotherinfectious agent. One example, for illustrative purposes, includes achimeric protein made from fusing the cytoplasmic tail and/ortransmembrane domain of an influenza HA protein from one strain to theextracellular domain of an influenza NA protein from a different strain.

As used herein, the term “derived from” refers to the origin or source,and may include naturally occurring, recombinant, unpurified, orpurified molecules. The proteins and molecules of the present inventionmay be derived from influenza or non-influenza molecules.

The term “infectious agent” refers to microorganisms that cause aninfection in a vertebrate. Infectious agents can be viruses, fungi,bacteria and/or parasites. A protein that may be expressed on thesurface of VLPs can be derived from viruses, fungi, bacteria and/orparasites. The proteins derived from viruses, fungi, bacteria and/orparasites can induce an immune response (cellular and/or humoral) in avertebrate that will prevent, treat, manage and/or ameliorate aninfectious disease in said vertebrate.

As used herein the term “avian influenza virus” refers to influenzaviruses found chiefly in birds but that can also infect humans or otheranimals. In some instances, avian influenza viruses may be transmittedor spread from one human to another. An avian influenza virus thatinfects humans has the potential to cause an influenza pandemic, i.e.,morbidity and/or mortality in humans. A pandemic occurs when a newstrain of influenza virus (a virus in which humans have no naturalimmunity) emerges, spreading beyond individual localities, possiblyaround the globe, and infecting many humans at once.

As used herein the term “seasonal influenza virus” refers to theinfluenza viral strains that have been determined to be passing withinthe human population for a given influenza season based onepidemiological surveys conducted by National Influenza Centersworldwide. These epidemiological studies, and some isolated influenzaviruses, are sent to one of four World Health Organization (WHO)reference laboratories, one of which is at the Centers for DiseaseControl and Prevention (CDC) in Atlanta for detailed testing. Theselaboratories test how well antibodies made to the current vaccine reactto the circulating virus and new flu viruses. This information, alongwith information about flu activity, is summarized and presented to anadvisory committee of the U.S. Food and Drug Administration (FDA) and ata WHO meeting. These meetings result in the selection of three viruses(two subtypes of influenza A viruses and one influenza B virus) to gointo flu vaccines for the following fall and winter. The selectionoccurs in February for the northern hemisphere and in September for thesouthern hemisphere. Usually, one or two of the three virus strains inthe vaccine changes each year.

As used herein, the term “antigenic protein” means a protein that iscapable of stimulating an immune response in a vertebrate.

As used herein, the term “vaccine” generally refers to a preparation ofdead or weakened pathogens, or of derived antigenic determinants, thatis used to induce formation of antibodies or immunity against thepathogen. A vaccine is given to provide immunity to the disease, forexample, influenza, which is caused by influenza viruses. The presentinvention provides vaccine compositions that are immunogenic and provideprotection. In addition, the term “vaccine” also refers to a suspensionor solution of an immunogen (e.g. VLP) that is administered to avertebrate to produce protective immunity, e.g., immunity that reducesthe severity of disease associated with infection or prevents aproductive infection.

As used herein, the term “antigenic formulation” or “antigeniccomposition” refers to a preparation which, when administered to avertebrate, especially a bird or a mammal, will induce a detectableimmune response.

As used herein, the term “effective amount” refers to an amount of VLPsnecessary or sufficient to realize a desired biologic effect. Aneffective amount of the composition would be the amount that achieves aselected result, and such an amount could be determined as a matter ofroutine by a person skilled in the art. For example, an effective amountfor preventing, treating and/or ameliorating an infection could be thatamount necessary to cause activation of the immune system, resulting inthe development of an antigen specific immune response upon exposure toVLPs of the invention. The term is also synonymous with “sufficientamount.”

As used herein the term “adjuvant” refers to a compound that, when usedin combination with a specific immunogen (e.g. a VLP) in a formulation,augments or otherwise alters or modifies the resultant immune response.Modification of the immune response includes intensification orbroadening the specificity of either or both antibody and cellularimmune responses. Modification of the immune response can also meandecreasing or suppressing certain antigen-specific immune responses.

As used herein the term “immune stimulator” refers to a compound thatenhances an immune response via the body's own chemical messengers(cytokines). These molecules comprise various cytokines, lymphokines andchemokines with immunostimulatory, immunopotentiating, andpro-inflammatory activities, such as interleukins (e.g., IL-1, IL-2,IL-3, IL-4, IL-12, IL-13); growth factors (e.g., granulocyte-macrophage(GM)-colony stimulating factor (CSF)); and other immunostimulatorymolecules, such as macrophage inflammatory factor, Flt3 ligand, B7.1;B7.2, etc. The immune stimulator molecules can be administered in thesame formulation as the influenza VLPs, or can be administeredseparately. Either the protein or an expression vector encoding theprotein can be administered to produce an immunostimulatory effect.

As used herein the term “substantial immunity” refers to an immuneresponse in which administration of VLPs of the invention to avertebrate induces the immune system in said vertebrate which results inthe prevention of infection (e.g. influenza infection), amelioration ofinfection, or reduction of at least one symptom related to the infectionin said vertebrate.

As used herein, the term “protective immunity” or “protective immuneresponse” refers to immunity or eliciting an immune response against aninfectious agent, which is exhibited by a vertebrate (e.g., a human),that prevents or ameliorates an infection or reduces at least onesymptom thereof.

As use herein, the term “vertebrate” or “subject” or “patient” refers toany member of the subphylum cordata, including, without limitation,humans and other primates, including non-human primates such aschimpanzees and other apes and monkey species. Farm animals such ascattle, sheep, pigs, goats and horses; domestic mammals such as dogs andcats; laboratory animals including rodents such as mice, rats and guineapigs; birds, including domestic, wild and game birds such as chickens,turkeys and other gallinaceous birds, ducks, geese, and the like arealso non-limiting examples. The terms “mammals” and “animals” areincluded in this definition. Both adult and newborn individuals areintended to be covered.

Influenza remains a pervasive public health concern despite theavailability of specific inactivated virus vaccines that are 60-80%effective under optimal conditions. When these vaccines are effective,illness is usually averted by preventing viral infection. The lack ofeffective influenza vaccine programs is partially due to the relativelyshort persistence of immunity elicited by the current vaccines.Restricted use of these vaccines because of vaccine reactogenicity andside effects in young children, elderly, and people with allergies tocomponents of eggs, which are used in manufacturing of commerciallylicensed inactivated virus influenza vaccines, also contributes to thepersistence of infection with influenza virus.

Vaccine failure can occur as a result of accumulated antigenicdifferences (antigenic shift and antigenic drift), in the HA and NAproteins leading to the emergence of different viral strains. Forexample, avian influenza virus type A H9N2 co-circulated with humaninfluenza virus type A Sydney/97 (H3N2) in pigs and led to geneticreassortment and emergence of new strains of human influenza virus withpandemic potential (Peiris et al., 2001). In the event of such antigenicshift, it is unlikely that current vaccines would provide adequateprotection.

Additionally, inactivated influenza virus vaccines often lack proper HAand NA conformational epitopes, which elicit neutralizing antibodies andplay a major role in protection against disease. Thus, inactivated viralvaccines, as well as some recombinant monomeric influenza subunitprotein vaccines, deliver inadequate protection. On the other hand,macromolecular protein structures, such as capsomers, subviralparticles, and/or VLPs, include multiple copies of native proteinsexhibiting conformational epitopes, which are advantageous for optimalvaccine immunogenicity.

VLPs of the Invention and Methods of Making VLPs

The inventors have discovered that expressing an influenza membraneprotein, such as M2, HA, or NA, in the absence of influenza matrix M1protein leads to the formation of VLPs. Alternatively, expression ofchimeric influenza proteins that comprise influenza cytoplasmic and/ortransmembrane domains in the absence of M1 matrix protein can also leadto VLP formation. Chimeric proteins can be constructed from either thetransmembrane domain or cytoplasmic tails of Orthomyxovirusmembraneproteins, e.g. influenza, fused to extracellular domains from antigenicproteins derived from other viral strains or other infectious agents.Thus, VLPs of the invention are useful for preparing vaccines againstinfectious agents as well as influenza viruses.

One advantageous feature of the invention is the ability to replace thesurface glycoproteins with different subtypes of HA, NA, and/orantigenic proteins from other infectious agents expressed in the VLPs.There are 16 different HA proteins and 9 different NA proteins, all ofwhich have been found among wild birds. Wild birds are the primarynatural reservoir for all types of influenza A viruses and are thoughtto be the source of all types of influenza A viruses in all othervertebrates. Subtypes of influenza viruses are classified by changes inthe HA and NA proteins on their surface. Many different combinations ofHA and NA proteins are possible. Each combination represents a differenttype of influenza A virus. In addition, each type can be furtherclassified into strains based on different mutations found in each ofits 8 genes. As antigenic variants of HA and NA are identified, the VLPscan be updated to include these new variants (e.g. for seasonalinfluenza vaccines). In addition, surface glycoproteins from potentiallypandemic viruses, such as H5N1, or other HA, NA combinations withpandemic potential could be incorporated into VLPs without concern ofreleasing genes that had not circulated in humans for several decades,since the VLPs are not infectious, do not replicate, and cannot causedisease. The VLPs of the invention can also contain antigenic proteinsfrom other infectious agents, thus allowing for the development ofvaccines for other human or animal pathogens.

The present invention provides purified VLPs comprising at least onechimeric Orthomyxovirus membrane protein, wherein the VLP does notcontain viral matrix or core protein. In another embodiment, the presentinvention provides purified VLPs comprising at least one chimericinfluenza membrane protein, wherein the VLP does not contain aninfluenza matrix (M1) protein. A chimeric protein is a protein thatcontains a fragment of an Orthomyxovirus protein, e.g. influenza, fusedto a heterologous protein. The heterologous protein may be a proteinderived from another strain of influenza or a protein derived fromanother infectious agent. In one embodiment, said chimeric proteincomprises the cytoplasmic tail of an influenza membrane protein fused toa heterologous protein. In another embodiment, said chimeric proteincomprises the transmembrane domain of an influenza membrane proteinfused to a heterologous protein. The cytoplasmic tails and transmembranedomains included in the chimeric proteins can be derived from influenzamembrane proteins HA, NA, or M2. In another embodiment, thetransmembrane domain and/or cytoplasmic tail of said influenza membraneproteins (e.g. HA and/or NA protein) extends from the N or C-terminus toapproximately 0, 1, 2, 3 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16,17, 18, 19, 20 to about 50 amino acids past the transmembrane domain andis fused to said protein from another infectious agent. In anotherembodiment, the portion of the protein from another infectious agentthat comprises a cytoplasmic and the transmembrane domain is replacedwith a cytoplasmic and/or transmembrane domain from said influenzamembrane protein (e.g. avian and/or seasonal influenza NA and/or HA). Inanother embodiment, said chimeric protein comprises a spacer between thecytoplasmic and/or transmembrane domain from said influenza protein andsaid heterologous protein. Said spacer can be approximately 0, 1, 2, 34, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 to about 50amino acids. In another embodiment, said VLPs comprise differentproteins from an infectious agent to make a multivalent VLP. One exampleincludes a VLP comprising at least one RSV protein and at least oneinfluenza protein. Many other combinations are possible.

Examples of cytoplasmic and/or transmembrane domains that can be fusedto heterologous proteins are listed on Table 1 below. Note that theseare only examples and are no way limited to those specific sequences. Ina further embodiment, the cytoplasmic and/or transmembrane can bepeptide fragments or peptide variants of said cytoplasmic and/ortransmembrane. These fragments will retain the ability to drive VLPformation and/or drive a chimeric protein to the host's cell membrane.The peptide fragments are at least about 1, least about 2, least about3, least about 4, at least 5, at least 6, at least 7, at least 8, atleast 9, at least 10, at least 11, at least 12, at least 13, at least14, at least 15, at least 20, at least 25, at least 30, at least 35, orat least about 40, at least about 50, at least about 55, at least about60 or at least about 70 or more amino acids in length fused to the Nand/or C terminus domain of a heterologous protein.

TABLE 1 Putative Cytoplasmic/Transmembrane domains of Influenza ProteinsSEQ Influenza ID Protein Transmembrane Domain Cytoplasmic Domain NO HALSIYSTVASSLALAIMMAGLSLW MCSNGSLQCRICI 1 M2 PLTIAANIIGILHLTLWILDRLFFKCIYRRFKYGLKGGPSTEGVPK 2 SMREEYRKEQQSAVDADDGHFVSIELE NAIITIGSICMVIGIVSLMLQIGNM MNPNQK 3

Methods to determine if cytoplasmic and/or transmembranes domains and/ortheir fragments fused to heterologous proteins will drive VLP formationand/or express said heterologous protein on the VLPs are known in theart and are described below. One example comprises seeding Sf9 cells(non-infected) into shaker flasks, allowing the cells to expand andinfecting said cells with recombinant baculovirus comprising at leastone chimeric protein described above. Once infection has occurred, thechimeric proteins are expressed from the recombinant baculovirus genome.If VLPs are formed, said VLPs can be isolated by passing the celllysates from infected cells through a 20%-60% sucrose density gradient.Fractions in which VLPs are expected to equilibrate (30% sucrosefraction) can be run on an SDS-PAGE gel and subsequently analyzed bywestern blot with antibodies for the specific heterologous protein. Aband on the western blot is an indication of VLP formation.

Some non-limiting examples of chimeric proteins of the invention includethe cytoplasmic tail or transmembrane domain of influenza HA proteinfused to a fragment of an antigenic heterologous protein, such as aglycoprotein from Varicella Zoster virus (gE, gI, gH, and gB), S proteinfrom a coronavirus (an agent that causes SARS), a surface protein fromRespiratory syncytial virus (F and G proteins), or a membrane protein(HA, NA, M2 proteins) from a different strain of influenza than the HAprotein from which the cytoplasmic tail or transmembrane domain isderived. Other examples of infectious agents from which antigenicproteins can be derived to make chimeric proteins of the invention arelisted below. In another embodiment, said VLP further comprises anenzymatically active influenza NA protein or homologous protein.

In another embodiment, said VLPs further comprise at least oneadditional protein from an infectious agent. Infectious agents can beviruses, bacteria, parasites and/or fungi. The proteins derived fromthese microorganisms can be expressed on the surface of the VLPs. Theseproteins can induce an immune response (cellular and/or humoral) in avertebrate, which will prevent, treat, manage and/or ameliorate aninfectious disease in said vertebrate. The infectious agent protein maybe expressed as a chimeric protein comprising a cytoplasmic and/ortransmembrane domain of an Orthomyxovirus protein. In anotherembodiment, the infectious agent protein may be expressed as a chimericprotein comprising a cytoplasmic and/or transmembrane domain of aninfluenza membrane protein as discussed above.

Non-limiting examples of viruses from which said infectious agentproteins can be derived from are the following: coronavirus (e.g. SARS),hepatitis viruses A, B, C, D & E3, human immunodeficiency virus (HIV),herpes viruses 1, 2, 6 & 7, cytomegalovirus, varicella zoster, papillomavirus, Epstein Barr virus, adenoviruses, bunya viruses (e.g. hantavirus), coxsakie viruses, picoma viruses, rotaviruses, rhinoviruses,rubella virus, mumps virus, measles virus, Rubella virus, polio virus(multiple types), adeno virus (multiple types), parainfluenza virus(multiple types), avian influenza (various types), shipping fever virus,Western and Eastern equine encephalomyelitis, Japaneseencephalomyelitis, fowl pox, rabies virus, slow brain viruses, roussarcoma virus, Papovaviridae, Parvoviridae, Picornaviridae, Poxyiridae(such as Smallpox or Vaccinia), Reoviridae (e.g., Rotavirus),Retroviridae (HTLV-I, HTLV-II, Lentivirus), Togaviridae (e.g.,Rubivirus), Newcastle disease virus, West Nile fever virus, Tick borneencephalitis, yellow fever, chikungunya virus, respiratory syncytialvirus, and dengue virus (all serotypes).

In another embodiment, the specific proteins from viruses may comprise:HA and/or NA from various strains of influenza virus (including avian),S protein from coronavirus, gp 160, gp140 and/or gp41 from HIV, F or Gproteins from respiratory syncytial virus, E and preM/M from yellowfever virus, Dengue (all serotypes) or any flavivirus. Also included areany protein from a virus that can induce an immune response (cellularand/or humoral) in a vertebrate that can prevent, treat, manage and/orameliorate an infectious disease in said vertebrate.

Non-limiting examples of bacteria from which said infectious agentproteins can be derived from are the following: B. pertussis, Leptospirapomona, S. paratyphi A and B, C. diphtheriae, C. tetani, C. botulinum,C. perfringens, C. feseri and other gas gangrene bacteria, B. anthracis,P. pestis, P. multocida, Neisseria meningitidis, N. gonorrheae,Hemophilus influenzae, Actinomyces (e.g., Norcardia), Acinetobacter,Bacillaceae (e.g., Bacillus anthrasis), Bacteroides (e.g., Bacteroidesfragilis), Blastomycosis, Bordetella, Borrelia (e.g., Borreliaburgdorferi), Brucella, Campylobacter, Chlamydia, Coccidioides,Corynebacterium (e.g., Corynebacterium diptheriae), E. coli (e.g.,Enterotoxigenic E. coli and Enterohemorrhagic E. coli), Enterobacter(e.g. Enterobacter aerogenes), Enterobacteriaceae (Klebsiella,Salmonella (e.g., Salmonella typhi, Salmonella enteritidis, Serratia,Yersinia, Shigella), Erysipelothrix, Haemophilus (e.g., Haemophilusinfluenza type B), Helicobacter, Legionella (e.g., Legionellapneumophila), Leptospira, Listeria (e.g., Listeria monocytogenes),Mycoplasma, Mycobacterium (e.g., Mycobacterium leprae and Mycobacteriumtuberculosis), Vibrio (e.g., Vibrio cholerae), Pasteurellacea, Proteus,Pseudomonas (e.g., Pseudomonas aeruginosa), Rickettsiaceae, Spirochetes(e.g., Treponema spp., Leptospira spp., Borrelia spp.), Shigella spp.,Meningiococcus, Pneumococcus and Streptococcus (e.g., Streptococcuspneumoniae and Groups A, B, and C Streptococci), Ureaplasmas. Treponemapollidum, Staphylococcus aureus, Pasteurella haemolytica,Corynebacterium diptheriae toxoid, Meningococcal polysaccharide,Bordetella pertusis, Streptococcus pneumoniae, Clostridium tetanitoxoid, and Mycobacterium bovis.

Non-limiting examples of parasites from which said infectious agentproteins can be derived from are the following: leishmaniasis(Leishmania tropica mexicana, Leishmania tropica, Leishmania major,Leishmania aethiopica, Leishmania braziliensis, Leishmania donovani,Leishmania infantum, Leishmania chagasi), trypanosomiasis (Trypanosomabrucei gambiense, Trypanosoma brucei rhodesiense), toxoplasmosis(Toxoplasma gondii), schistosomiasis (Schistosoma haematobium,Schistosoma japonicum, Schistosoma mansoni, Schistosoma mekongi,Schistosoma intercalatum), malaria (Plasmodium virax, Plasmodiumfalciparium, Plasmodium malariae and Plasmodium ovale) Amebiasis(Entamoeba histolytica), Babesiosis (Babesiosis microti),Cryptosporidiosis (Cryptosporidium parvum), Dientamoebiasis (Dientamoebafragilis), Giardiasis (Giardia lamblia), Helminthiasis and Trichomonas(Trichomonas vaginalis).

Non-limiting examples of fungi from which said infectious agent proteinscan be derived are from the following: Absidia (e.g. Absidiacorymbifera), Ajellomyces (e.g. Ajellomyces capsulatus, Ajellomycesdermatitidis), Arthroderma (e.g. Arthroderma benhamiae, Arthrodermafulvum, Arthroderma gypseum, Arthroderma incurvatum, Arthroderma otae,Arthroderma vanbreuseghemii), Aspergillus (e.g. Aspergillus fumigatus,Aspergillus niger), Candida (e.g. Candida albicans, Candida albicansvar. stellatoidea, Candida dublinensis, Candida glabrata, Candidaguilliermondii (Pichia guilliermondii), Candida krusei (Issatschenkiaorientalis), Candida parapsilosis, Candida pelliculosa (Pichia anomala),Candida tropicalis), Coccidioides (e.g. Coccidioides immitis),Cryptococcus (e.g. Cryptococcus neoformans (Filobasidiella neoformans),Histoplasma (e.g. Histoplasma capsulatum (Ajellomyces capsulatus),Microsporum (e.g. Microsporum canis (Arthroderma otae), Microsporumfulvum (Arthroderma fulvum), Microsporum gypseum, Genus Pichia (e.g.Pichia anomala, Pichia guilliermondii), Pneumocystis (e.g. Pneumocystisjirovecii), Cryptosporidium, Malassezia furfur, Paracoccidiodes. Theabove lists are meant to be illustrative and by no means are meant tolimit the invention to those particular bacterial, viral, fungal orparasitic organisms.

In another embodiment, said VLPs do not contain a viral matrix or coreprotein. A viral matrix protein is a protein that organizes andmaintains virion structure. Viral matrix proteins usually interactdirectly with cellular membranes and can be involved in the buddingprocess. Viral core proteins are proteins that make up part of thenucelocapsid and typically are directly associated with the viralnucleic acid. Examples include RSV M and retrovirus gag proteins.

The invention also provides a purified VLP comprising at least oneinfluenza membrane protein, wherein the VLP does not contain aninfluenza matrix (M1) protein. In one embodiment, said VLP furthercomprises at least one additional protein from an infectious agent. Inanother embodiment, said influenza membrane protein is HA. In anotherembodiment, said HA is a seasonal or avian HA. In another embodiment,said VLP does not contain a viral matrix or core protein. The influenzamembrane proteins include HA, NA, and M2 and can be derived frominfluenza B or any strain of influenza A.

In another embodiment, said VLP further comprises an influenza NAprotein. The NA protein and at least one influenza membrane protein caneither be derived from the same influenza strain or derived fromdifferent strains. In some embodiments, said VLP comprises a HA from anavian, pandemic and/or seasonal influenza virus and a NA from an avian,pandemic and/or seasonal influenza virus, wherein said HA is selectedfrom the group consisting of H1, H2, H3, H4, H5, H6, H7 H8, H9, H10,H11, H12, H13, H14, H15 and H16 and said NA is selected from the groupconsisting of N1, N2, N3, N4, N5, N6, N7, N8 and N9. In one embodiment,said VLP comprises HA and NA proteins, which are both derived from theinfluenza H5N1 virus subtype. In other embodiments, said HA and NAproteins are derived from different influenza subtypes. In anotherembodiment, said NA protein has enzymatic activity.

The invention also encompasses variants of the said influenza proteinsand chimeric proteins expressed on or in the VLPs of the invention. Thevariants may contain alterations in the amino acid sequences of theconstituent proteins. The term “variant” with respect to a polypeptiderefers to an amino acid sequence that is altered by one or more aminoacids with respect to a reference sequence. The variant can have“conservative” changes, wherein a substituted amino acid has similarstructural or chemical properties, e.g., replacement of leucine withisoleucine. Alternatively, a variant can have “nonconservative” changes,e.g., replacement of a glycine with a tryptophan. Analogous minorvariations can also include amino acid deletion or insertion, or both.Guidance in determining which amino acid residues can be substituted,inserted, or deleted without eliminating biological or immunologicalactivity can be found using computer programs well known in the art, forexample, DNASTAR software.

Natural variants can occur due to antigenic drifts. Antigenic drifts aresmall changes in the viral proteins that happen continually over time.Thus, a person infected with a particular flu virus strain developsantibody against that virus, as newer virus strains appear, theantibodies against the older strains no longer recognize the newer virusand reinfection can occur. This is why there is a new vaccine forinfluenza each season. In addition, some changes in an influenza viruscan cause influenza virus to cross species. For example, some avianinfluenza viruses developed genetic variations associated with thecapability of crossing the species barrier. Such a virus is capable ofcausing a pandemic because people have no natural immunity to the virusand the virus can easily spread from person to person. These naturallyoccurring variations of the influenza proteins are an embodiment of theinvention.

General texts which describe molecular biological techniques, which areapplicable to the present invention, such as cloning, mutation, cellculture and the like, include Berger and Kimmel, Guide to MolecularCloning Techniques, Methods in Enzymology volume 152 Academic Press,Inc., San Diego, Calif. (Berger); Sambrook et al., Molecular Cloning—ALaboratory Manual (3rd Ed.), Vol. 1-3, Cold Spring Harbor Laboratory,Cold Spring Harbor, N.Y., 2000 (“Sambrook”) and Current Protocols inMolecular Biology, F. M. Ausubel et al., eds., Current Protocols, ajoint venture between Greene Publishing Associates, Inc. and John Wiley& Sons, Inc., (“Ausubel”). These texts describe mutagenesis, the use ofvectors, promoters and many other relevant topics related to, e.g., thecloning and mutation of influenza proteins or fragments thereof. Thus,the invention also encompasses using known methods of proteinengineering and recombinant DNA technology to improve or alter thecharacteristics of the influenza proteins expressed on or in the VLPs ofthe invention. Various types of mutagenesis can be used to produceand/or isolate variant influenza proteins or antigenic proteins derivedfrom other infectious agents and/or to further modify/mutate thepolypeptides of the invention. They include but are not limited tosite-directed, random point mutagenesis, homologous recombination (DNAshuffling), mutagenesis using uracil containing templates,oligonucleotide-directed mutagenesis, phosphorothioate-modified DNAmutagenesis, mutagenesis using gapped duplex DNA or the like. Additionalsuitable methods include point mismatch repair, mutagenesis usingrepair-deficient host strains, restriction-selection andrestriction-purification, deletion mutagenesis, mutagenesis by totalgene synthesis, double-strand break repair, and the like. Mutagenesis,e.g., involving chimeric constructs, is also included in the presentinvention. In one embodiment, mutagenesis can be guided by knowninformation of the naturally occurring molecule or altered or mutatednaturally occurring molecule, e.g., sequence, sequence comparisons,physical properties, crystal structure or the like.

The invention further comprises influenza protein variants which showsubstantial biological activity, e.g., able to elicit an effectiveantibody response when expressed on or in a VLP. Such variants includedeletions, insertions, inversions, repeats, and substitutions selectedaccording to general rules known in the art so as to have little effecton activity.

Methods of cloning said influenza proteins are known in the art. Forexample, the influenza gene encoding a specific influenza protein can beisolated by RT-PCR from polyadenylated mRNA extracted from cells whichhad been infected with an influenza virus. The resulting product genecan be cloned as a DNA insert into a vector. The term “vector” refers tothe means by which a nucleic acid can be propagated and/or transferredbetween organisms, cells, or cellular components. Vectors includeplasmids, viruses, bacteriophages, pro-viruses, phagemids, transposons,artificial chromosomes, and the like, that replicate autonomously or canintegrate into a chromosome of a host cell. A vector can also be a nakedRNA polynucleotide, a naked DNA polynucleotide, a polynucleotidecomposed of both DNA and RNA within the same strand, apoly-lysine-conjugated DNA or RNA, a peptide-conjugated DNA or RNA, aliposome-conjugated DNA, or the like, that is not autonomouslyreplicating. In many, but not all, common embodiments, the vectors ofthe present invention are plasmids or bacmids.

Thus, the invention comprises nucleotides that encode influenza membraneproteins, including chimeric molecules, cloned into an expression vectorthat can be expressed in a cell that induces the formation of VLPs ofthe invention. An “expression vector” is a vector, such as a plasmidthat is capable of promoting expression, as well as replication of anucleic acid incorporated therein. Typically, the nucleic acid to beexpressed is “operably linked” to a promoter and/or enhancer, and issubject to transcription regulatory control by the promoter and/orenhancer. In one embodiment, said nucleotides encode for a chimericprotein (as discussed above). In another embodiment, said vectorcomprises nucleotides that encode the HA and/or NA influenza membraneproteins. In another embodiment, said vector comprises nucleotides thatencode the M2 influenza membrane protein. In another embodiment, saidvector comprises nucleotides that encode a chimeric protein and anantigenic protein from another infectious agent. In another embodiment,said vector comprises nucleotides that encode HA protein and anantigenic protein from another infectious agent. In a preferredembodiment, the expression vector is a baculovirus vector. After thenucleotides encoding said influenza proteins or chimeric proteins havebeen cloned, said nucleotides can be further manipulated. For example, aperson with skill in the art can mutate specific bases in the codingregion to produce variants. The variants may contain alterations in thecoding regions, non-coding regions, or both. Such variants may increasethe immunogenicity of an influenza protein or chimeric protein or removea splice site from a protein or RNA. For example, in one embodiment, theHA is engineered to remove or mutate the cleavage site. For example,wild type H5 HA has a cleavage site that contains multiple basic aminoacids (RRRKR (SEQ ID NO. 5)). This wild type sequence makes the HA moresusceptible to multiple ubiquitous proteases that may be present in hostcells or systems expressing these HAs. In one embodiment, removing theseamino acids can reduce the susceptibility of the HA to variousproteases. In another embodiment, the cleavage site can be mutated toremove the cleavage site (e.g. mutate to RESR (SEQ ID NO. 6)).

In some embodiments, mutations can be made which produce silentsubstitutions, additions, or deletions, but do not alter the propertiesor activities of the encoded protein or how the proteins are made.Nucleotide variants can be produced for a variety of reasons, e.g., tooptimize codon expression for a particular host (change codons in thehuman mRNA to those preferred by insect cells such as Sf9 cells). SeeU.S. patent publication 2005/0118191, herein incorporated by referencein its entirety for all purposes.

In addition, the nucleotides can be sequenced to ensure that the correctcoding regions were cloned and do not contain any unwanted mutations.The nucleotides can be subcloned into an expression vector (e.g.baculovirus) for expression in any cell. The above is only one exampleof how the influenza viral proteins can be cloned. A person with skillin the art understands that additional methods are available and arepossible.

The invention also provides for constructs and/or vectors that comprisenucleotides that encode for influenza genes, including HA, NA, M2, orportions thereof, and/or any chimeric molecule described above. Thevector may be, for example, a phage, plasmid, viral, or retroviralvector. The constructs and/or vectors that encode influenza viral genes,including HA, NA, M2, or portions thereof, and/or any chimeric moleculedescribed above, should be operatively linked to an appropriatepromoter, such as the AcMNPV polyhedrin promoter (or other baculoviruspromoter), phage lambda PL promoter, the E. coli lac, phoA and tacpromoters, the SV40 early and late promoters, and promoters ofretroviral LTRs are non-limiting examples. Other suitable promoters willbe known to the skilled artisan depending on the host cell and/or therate of expression desired. The expression constructs will furthercontain sites for transcription initiation, termination, and, in thetranscribed region, a ribosome binding site for translation. The codingportion of the transcripts expressed by the constructs will preferablyinclude a translation initiating codon at the beginning and atermination codon appropriately positioned at the end of the polypeptideto be translated.

The expression vectors will preferably include at least one selectablemarker. Such markers include dihydrofolate reductase, G418 or neomycinresistance for eukaryotic cell culture and tetracycline, kanamycin orampicillin resistance genes for culturing in E. coli and other bacteria.Among vectors preferred are virus vectors, such as baculovirus, poxvirus(e.g., vaccinia virus, avipox virus, canarypox virus, fowlpox virus,raccoonpox virus, swinepox virus, etc.), adenovirus (e.g., canineadenovirus), herpesvirus, and retrovirus. Other vectors that can be usedwith the invention comprise vectors for use in bacteria, which includepQE70, pQE60 and pQE-9, pBluescript vectors, Phagescript vectors, pNH8A,pNH16a, pNH18A, pNH46A, ptrc99a, pKK223-3, pKK233-3, pDR540, and pRIT5.Among preferred eukaryotic vectors are pFastBacl pWINEO, pSV2CAT, pOG44,pXT1 and pSG, pSVK3, pBPV, pMSG, and pSVL. Other suitable vectors willbe readily apparent to the skilled artisan. In one embodiment, saidvector that comprises nucleotides encoding for influenza viral genes,including HA, NA, M2, or portions thereof, and/or any chimeric molecule,is pFastBac.

Next, the recombinant vector can be transfected, infected, ortransformed into a suitable host cell. Thus, the invention provides forhost cells which comprise a vector (or vectors) that contain nucleicacids which code for HA, NA, M2, or any chimeric molecule describedabove and permit the expression of those genes in said host cell underconditions which allow the formation of VLPs.

In one embodiment, the recombinant constructs mentioned above could beused to transfect, infect, or transform eukaryotic cells and/orprokaryotic cells to express HA, NA, M2, or any chimeric proteindescribed above. Among eukaryotic host cells are yeast, insect, avian,plant, C. elegans (or nematode) and mammalian host cells. Non limitingexamples of insect cells are, Spodoptera frugiperda (Sf) cells, e.g.Sf9, Sf21, Trichoplusia ni cells, e.g. High Five cells, and DrosophilaS2 cells. Examples of fungi (including yeast) host cells are S.cerevisiae, Kluyveromyces lactis (K. lactis), species of Candidaincluding C. albicans and C. glabrata, Aspergillus nidulans,Schizosaccharomyces pombe (S. pombe), Pichia pastoris, and Yarrowialipolytica. Examples of mammalian cells are COS cells, baby hamsterkidney cells, mouse L cells, LNCaP cells, Chinese hamster ovary (CHO)cells, human embryonic kidney (HEK) cells, and African green monkeycells, CV1 cells, HeLa cells, MDCK cells, Vero and Hep-2 cells. Xenopuslaevis oocytes, or other cells of amphibian origin, may also be used.Prokaryotic host cells include bacterial cells, for example, E. coli, B.subtilis, and mycobacteria.

Vectors, e.g., vectors comprising HA, NA, M2 or chimericpolynucleotides, can be transfected into host cells according to methodswell known in the art. For example, introducing nucleic acids intoeukaryotic cells can be by calcium phosphate co-precipitation,electroporation, microinjection, lipofection, and transfection employingpolyamine transfection reagents. In one embodiment, the said vector is arecombinant baculovirus. In another embodiment, said recombinantbaculovirus is transfected into a eukaryotic cell. In a preferredembodiment, said cell is an insect cell. In another embodiment, saidinsect cell is a Sf9 cell.

In another embodiment, said vector and/or host cell comprise nucleotideswhich encode an avian, pandemic and/or seasonal influenza virus HAprotein selected from the group consisting of H1, H2, H3, H4, H5, H6,H7, H8, H9, H10, H11, H12, H13, H14, H15 and H16. In another embodiment,said vector and/or host cells comprise nucleotides which encode an NAprotein which is selected from the group consisting of N1, N2, N3, N4,N5, N6, N7, N8 and N9. In another embodiment, said vector and/or hostcell comprises influenza HA, and/or NA. In another embodiment, saidvector and/or host cell comprises influenza HA, NA, and an antigenicprotein from another infectious agent. In another embodiment, saidvector and/or host cell comprises at least onechimeric protein describedabove. These vector and/or host cells do not contain influenza M1protein or any other viral matrix or core proteins.

This invention also provides for constructs and methods that willincrease the efficiency of VLP production. For example, the nucleotidesthat encode HA, NA, M2, or chimeric proteins can be codon optimized fora specific cell type. For example, nucleic acids can be codon optimizedfor expression in Sf9 cells (see U.S. patent publication 2005/0118191,herein incorporated by reference in its entirety for all purposes).

The invention includes methods of making VLPs comprising expressing achimeric protein or an influenza membrane protein in a cell, wherein thecell does not contain or express an influenza matrix (M1) protein; andpurifying the VLPs. Depending on the expression system and host cellselected, the VLPs are produced by growing host cells transformed by anexpression vector under conditions whereby the recombinant proteins areexpressed and VLPs are formed. The selection of the appropriate growthconditions is within the ordinary skill in the art.

Methods to grow cells engineered to produce VLPs of the inventioninclude, but are not limited to, batch, batch-fed, continuous andperfusion cell culture techniques. Cell culture means the growth andpropagation of cells in a bioreactor (a fermentation chamber) wherecells propagate and express protein (e.g. recombinant proteins) forpurification and isolation. Typically, cell culture is performed understerile, controlled temperature and atmospheric conditions in abioreactor. A bioreactor is a chamber used to culture cells in whichenvironmental conditions such as temperature, atmosphere, agitationand/or pH can be monitored. In one embodiment, said bioreactor is astainless steel chamber. In another embodiment, said bioreactor is apre-sterilized plastic bag (e.g. Cellbag®, Wave Biotech, Bridgewater,N.J.). In other embodiment, said pre-sterilized plastic bags are about50 L to 1000 L bags.

The VLPs are then isolated using methods that preserve the integritythereof, such as by gradient centrifugation, e.g., cesium chloride,sucrose and iodixanol, as well as standard purification techniquesincluding, e.g., ion exchange and gel filtration chromatography.

The following is an example of how VLPs of the invention may be made,isolated and purified. Usually VLPs are produced from recombinant celllines engineered to create a VLP when said cells are grown in cellculture (see above). Production of VLPs may be accomplished asillustrated in the Examples. A person of skill in the art wouldunderstand that there are additional methods that can be utilized tomake and purify VLPs of the invention, thus the invention is not limitedto the method described.

Production of VLPs of the invention can start by seeding Sf9 cells(non-infected) into shaker flasks, allowing the cells to expand andscaling up as the cells grow and multiply (for example from a 125-mlflask to a 50 L Wave bag). The medium used to grow the cells isformulated for the appropriate cell line (preferably serum free media,e.g. insect medium ExCell-420, JRH). Next, said cells are infected withrecombinant baculovirus at the most efficient multiplicity of infection(e.g. from about 1 to about 3 plaque forming units per cell). Onceinfection has occurred, the chimeric proteins or HA, NA or M2 proteinsare expressed from the recombinant baculovirus genome, self assembleinto VLPs and are secreted from the cells approximately 24 to 72 hourspost infection. Usually, infection is most efficient when the cells arein mid-log phase of growth (4−8×10⁶ cells/ml) and are at least about 90%viable.

VLPs of the invention can be harvested approximately 48 to 96 hours postinfection, when the levels of VLPs in the cell culture medium are nearthe maximum but before extensive cell lysis. The Sf9 cell density andviability at the time of harvest can be about 0.5×10⁶ cells/ml to about1.5×10⁶ cells/ml with at least 20% viability, as shown by dye exclusionassay. Next, the medium is removed and clarified. NaCl can be added tothe medium to a concentration of about 0.4 to about 1.0 M, preferably toabout 0.5 M, to avoid VLP aggregation. The removal of cells and cellulardebris from the cell culture medium containing VLPs of the invention canbe accomplished by tangential flow filtration (TFF) with a single use,pre-sterilized hollow fiber 0.5 or 1.00 μm filter cartridge or a similardevice.

Next, VLPs in the clarified culture medium can be concentrated byultrafiltration using a disposable, pre-sterilized 500,000 molecularweight cut off hollow fiber cartridge. The concentrated VLPs can bediafiltrated against 10 volumes pH 7.0 to 8.0 phosphate-buffered saline(PBS) containing 0.5 M NaCl to remove residual medium components.

The concentrated, diafiltered VLPs can be furthered purified on a 20% to60% discontinuous sucrose gradient in pH 7.2 PBS buffer with 0.5 M NaClby centrifugation at 6,500×g for 18 hours at about 4° C. to about 10° C.Usually VLPs will form a distinctive visible band between about 30% toabout 40% sucrose or at the interface (in a 20% and 60% step gradient)that can be collected from the gradient and stored. This product can bediluted to comprise 200 mM of NaCl in preparation for the next step inthe purification process. This product contains VLPs and may containintact baculovirus particles.

Further purification of VLPs can be achieved by anion exchangechromatography, or 44% isopycnic sucrose cushion centrifugation. Inanion exchange chromatography, the sample from the sucrose gradient (seeabove) is loaded into column containing a medium with an anion (e.g.Matrix Fractogel EMD TMAE) and eluded via a salt gradient (from about0.2 M to about 1.0 M of NaCl) that can separate the VLP from othercontaminates (e.g. baculovirus and DNA/RNA). In the sucrose cushionmethod, the sample comprising the VLPs is added to a 44% sucrose cushionand centrifuged for about 18 hours at 30,000 g. VLPs form a band at thetop of 44% sucrose, while baculovirus precipitates at the bottom andother contaminating proteins stay in the 0% sucrose layer at the top.The VLP peak or band is collected.

The intact baculovirus can be inactivated, if desired. Inactivation canbe accomplished by chemical methods, for example, formalin or β-propyllactone (BPL). Removal and/or inactivation of intact baculovirus canalso be largely accomplished by using selective precipitation andchromatographic methods known in the art, as exemplified above. Methodsof inactivation comprise incubating the sample containing the VLPs in0.2% of BPL for 3 hours at about 25° C. to about 27° C. The baculoviruscan also be inactivated by incubating the sample containing the VLPs at0.05% BPL at 4° C. for 3 days, then at 37° C. for one hour.

After the inactivation/removal step, the product comprising VLPs can berun through another diafiltration step to remove any reagent from theinactivation step and/or any residual sucrose, and to place the VLPsinto the desired buffer (e.g. PBS). The solution comprising VLPs can besterilized by methods known in the art (e.g. sterile filtration) andstored in the refrigerator or freezer.

The above techniques can be practiced across a variety of scales. Forexample, T-flasks, shake-flasks, spinner bottles, up to industrial sizedbioreactors. The bioreactors can comprise either a stainless steel tankor a pre-sterilized plastic bag (for example, the system sold by WaveBiotech, Bridgewater, N.J.). A person with skill in the art will knowwhat is most desirable for their purposes.

Expansion and production of baculovirus expression vectors and infectionof cells with recombinant baculovirus to produce recombinant influenzaVLPs can be accomplished in insect cells, for example Sf9 insect cellsas previously described. In a preferred embodiment, the cells are SF9infected with recombinant baculovirus engineered to produce influenzaVLPs.

Pharmaceutical or Vaccine Formulations and Administration

The pharmaceutical compositions useful herein contain a pharmaceuticallyacceptable carrier, including any suitable diluent or excipient, whichincludes any pharmaceutical agent that does not itself induce theproduction of an immune response harmful to the vertebrate receiving thecomposition, and which may be administered without undue toxicity and aVLP of the invention. As used herein, the term “pharmaceuticallyacceptable” means being approved by a regulatory agency of the Federalor a state government or listed in the U.S. Pharmacopia, EuropeanPharmacopia or other generally recognized pharmacopeia for use invertebrates, and more particularly in humans. These compositions can beuseful as a vaccine and/or antigenic compositions for inducing aprotective immune response in a vertebrate.

The invention provides a vaccine comprising VLPs that comprise at leastone influenza membrane protein, but do not contain an influenza matrix(M1) protein. In one embodiment, said influenza membrane protein is HA.In another embodiment, said HA protein is a seasonal or avian HA. Inanother embodiment, said vaccine comprises VLPs further comprising atleast one antigenic protein from an infectious agent. In anotherembodiment, said vaccine comprises VLPs further comprising influenza NAprotein. In another embodiment, said vaccine comprises VLPs comprisingHA and NA proteins derived from the influenza H5N1 subtype.

The invention also provides a vaccine comprising VLPs that comprise atleast one chimeric protein, but do not contain an influenza matrix (M1)protein. In one embodiment, the vaccine comprises VLPs comprising achimeric protein, wherein the chimeric protein contains the cytoplasmictail of an influenza membrane protein. In another embodiment, saidmembrane protein is HA. In another embodiment, said membrane protein isNA. In another embodiment, said membrane protein is M2. In anotherembodiment, said vaccine comprises VLPs further comprising at least oneantigenic protein from an infectious agent. In another embodiment, saidvaccine comprises VLPs comprising a chimeric protein, wherein thechimeric protein contains the transmembrane domain of an influenzamembrane protein. In another embodiment, said membrane protein is HA.

The invention includes an antigenic formulation comprising VLPs thatcomprise at least one influenza membrane protein, but do not contain aninfluenza matrix (M1) protein. In one embodiment, said influenzamembrane protein is HA. In another embodiment, said HA protein is aseasonal or avian HA. In another embodiment, said antigenic formulationcomprises VLPs further comprising at least one antigenic protein from aninfectious agent. In another embodiment, said antigenic formulationcomprises VLPs further comprising influenza NA protein. In anotherembodiment, said antigenic formulation comprises VLPs comprising HA andNA proteins derived from the influenza H5N1 subtype.

The invention also includes an antigenic formulation comprising VLPsthat comprise at least one chimeric protein, but do not contain aninfluenza matrix (M1) protein. In one embodiment, the antigenicformulation comprises VLPs comprising a chimeric protein, wherein thechimeric protein contains the cytoplasmic tail of an influenza membraneprotein. In another embodiment, said membrane protein is HA. In anotherembodiment, said membrane protein is NA. In another embodiment, saidmembrane protein is M2. In another embodiment, said antigenicformulation comprises VLPs further comprising at least one antigenicprotein from an infectious agent. In another embodiment, said antigenicformulation comprises VLPs comprising a chimeric protein, wherein thechimeric protein contains the transmembrane domain of an influenzamembrane protein. In another embodiment, said membrane protein is HA.

Said pharmaceutical formulations of the invention comprise VLPscomprising an influenza HA, NA, or M2 protein or any chimeric moleculedescribed above and a pharmaceutically acceptable carrier or excipient.Pharmaceutically acceptable carriers include but are not limited tosaline, buffered saline, dextrose, water, glycerol, sterile isotonicaqueous buffer, and combinations thereof. A thorough discussion ofpharmaceutically acceptable carriers, diluents, and other excipients ispresented in Remington's Pharmaceutical Sciences (Mack Pub. Co. N.J.current edition). The formulation should suit the mode ofadministration. In a preferred embodiment, the formulation is suitablefor administration to humans, preferably is sterile, non-particulateand/or non-pyrogenic.

In another embodiment, different chimeric VLPs are blended together tocreate a multivalent formulation. These VLPs may comprise VLPs HA and/orNA from different strains of influenza virus (e.g. influenza A and/orinfluenza B) or chimeric protein from different infectious agents (e.g.RSV, coronavirus, HIV). One example includes a formulation comprisingVLPs which comprising at least one RSV protein and at least oneinfluenza protein. Many other combinations are possible.

The composition, if desired, can also contain minor amounts of wettingor emulsifying agents, or pH buffering agents. The composition can be asolid form, such as a lyophilized powder suitable for reconstitution, aliquid solution, suspension, emulsion, tablet, pill, capsule, sustainedrelease formulation, or powder. Oral formulation can include standardcarriers such as pharmaceutical grades of mannitol, lactose, starch,magnesium stearate, sodium saccharine, cellulose, magnesium carbonate,etc.

The invention provides that the VLP formulation be packaged in ahermetically sealed container such as an ampoule or sachette indicatingthe quantity of composition. In one embodiment, the VLP composition issupplied as a liquid, in another embodiment, as a dry sterilizedlyophilized powder or water free concentrate in a hermetically sealedcontainer and can be reconstituted, e.g., with water or saline to theappropriate concentration for administration to a subject.

In an alternative embodiment, the VLP composition is supplied in liquidform in a hermetically sealed container indicating the quantity andconcentration of the VLP composition. Preferably, the liquid form of theVLP composition is supplied in a hermetically sealed container at leastabout 50 μg/ml, more preferably at least about 100 μg/ml, at least about200 μg/ml, at least 500 μg/ml, or at least 1 mg/ml.

Generally, VLPs of the invention are administered in an effective amountor quantity sufficient to stimulate an immune response against one ormore strains of influenza or another infectious agent from which theantigenic protein contained within the VLP is derived. Preferably,administration of the VLP of the invention elicits immunity againstinfluenza. Typically, the dose can be adjusted within this range basedon, e.g., age, physical condition, body weight, sex, diet, time ofadministration, and other clinical factors. The prophylactic vaccineformulation is systemically administered, e.g., by subcutaneous orintramuscular injection using a needle and syringe, or a needle-lessinjection device. Alternatively, the vaccine formulation is administeredintranasally, either by drops, large particle aerosol (greater thanabout 10 microns), or spray into the upper respiratory tract. While anyof the above routes of delivery results in an immune response,intranasal administration confers the added benefit of eliciting mucosalimmunity at the site of entry of many viruses, including influenza.

Thus, the invention also comprises a method of formulating a vaccine orantigenic composition that induces immunity to an infection or at leastone symptom thereof to a mammal, comprising adding to said formulationan effective dose of a VLP of the invention. In one embodiment, saidinfection is an influenza infection. An “effective dose” generallyrefers to the amount of VLPs of the invention sufficient to induceimmunity, to prevent and/or ameliorate an infection or to reduce atleast one symptom of an infection and/or to enhance the efficacy ofanother dose of a VLP. An effective dose may refer to the amount of VLPssufficient to delay or minimize the onset of an infection. An effectivedose may also refer to the amount of VLPs that provide a therapeuticbenefit in the treatment or management of an infection. Further, aneffective dose is the amount with respect to VLPs of the inventionalone, or in combination with other therapies, that provides atherapeutic benefit in the treatment or management of an infection. Aneffective dose may also be the amount sufficient to enhance a subject's(e.g., a human's) own immune response against a subsequent exposure toan infectious agent. Levels of immunity can be monitored, e.g., bymeasuring amounts of neutralizing secretory and/or serum antibodies,e.g., by plaque neutralization, complement fixation, enzyme-linkedimmunosorbent, or microneutralization assay. In the case of a vaccine,an “effective dose” is one that prevents disease and/or reduces theseverity of symptoms.

While stimulation of immunity with a single dose is preferred,additional dosages can be administered, by the same or different route,to achieve the desired effect. In neonates and infants, for example,multiple administrations may be required to elicit sufficient levels ofimmunity. Administration can continue at intervals throughout childhood,as necessary to maintain sufficient levels of protection againstinfections, e.g. influenza infection. Similarly, adults who areparticularly susceptible to repeated or serious infections, such as, forexample, health care workers, day care workers, family members of youngchildren, the elderly, and individuals with compromised cardiopulmonaryfunction may require multiple immunizations to establish and/or maintainprotective immune responses. Levels of induced immunity can bemonitored, for example, by measuring amounts of neutralizing secretoryand serum antibodies, and dosages adjusted or vaccinations repeated asnecessary to elicit and maintain desired levels of protection.

Methods of administering a composition comprising VLPs (vaccine and/orantigenic formulations) include, but are not limited to, parenteraladministration (e.g., intradermal, intramuscular, intravenous andsubcutaneous), epidural, and mucosal (e.g., intranasal and oral orpulmonary routes or by suppositories). In a specific embodiment,compositions of the present invention are administered orally,intradermally, intranasally, intramuscularly, intraperitoneally,intravenously, or subcutaneously. The compositions may be administeredby any convenient route, for example by infusion or bolus injection, byabsorption through epithelial or mucocutaneous linings (e.g., oralmucous, colon, conjunctiva, nasopharynx, oropharynx, vagina, urethra,urinary bladder and intestinal mucosa, etc.) and may be administeredtogether with other biologically active agents. In some embodiments,intranasal or other mucosal routes of administration of a compositioncomprising VLPs of the invention may induce an antibody or other immuneresponse that is substantially higher than other routes ofadministration. In another embodiment, intranasal or other mucosalroutes of administration of a composition comprising VLPs of theinvention may induce an antibody or other immune response that willinduce cross protection against other strains of influenza.Administration can be systemic or local.

Vaccines and/or antigenic formulations of the invention may also beadministered on a dosage schedule, for example, an initialadministration of the vaccine composition with subsequent boosteradministrations. In particular embodiments, a second dose of thecomposition is administered anywhere from two weeks to one year,preferably from about 1, about 2, about 3, about 4, about 5 to about 6months, after the initial administration. Additionally, a third dose maybe administered after the second dose and from about three months toabout two years, or even longer, preferably about 4, about 5, or about 6months, or about 7 months to about one year after the initialadministration. The third dose may be optionally administered when no orlow levels of specific immunoglobulins are detected in the serum and/orurine or mucosal secretions of the subject after the second dose. In apreferred embodiment, a second dose is administered about one monthafter the first administration and a third dose is administered aboutsix months after the first administration. In another embodiment, thesecond dose is administered about six months after the firstadministration. In another embodiment, said VLPs of the invention can beadministered as part of a combination therapy. For example, VLPs of theinvention can be formulated with other immunogenic compositions,antivirals and/or antibiotics.

The dosage of the pharmaceutical formulation can be determined readilyby the skilled artisan, for example, by first identifying doseseffective to elicit a prophylactic or therapeutic immune response, e.g.,by measuring the serum titer of virus specific immunoglobulins or bymeasuring the inhibitory ratio of antibodies in serum samples, or urinesamples, or mucosal secretions. Said dosages can be determined fromanimal studies. A non-limiting list of animals used to study theefficacy of vaccines include the guinea pig, hamster, ferrets,chinchilla, mouse and cotton rat. Most animals are not natural hosts toinfectious agents but can still serve in studies of various aspects ofthe disease. For example, any of the above animals can be dosed with avaccine candidate, e.g. VLPs of the invention, to partially characterizethe immune response induced, and/or to determine if any neutralizingantibodies have been produced. For example, many studies have beenconducted in the mouse model because mice are small in size and theirlow cost allows researchers to conduct studies on a larger scale.

In addition, human clinical studies can be performed to determine thepreferred effective dose for humans by a skilled artisan. Such clinicalstudies are routine and well known in the art. The precise dose to beemployed will also depend on the route of administration. Effectivedoses may be extrapolated from dose-response curves derived from invitro or animal test systems.

As also well known in the art, the immunogenicity of a particularcomposition can be enhanced by the use of non-specific stimulators ofthe immune response, known as adjuvants. Adjuvants have been usedexperimentally to promote a generalized increase in immunity againstunknown antigens (e.g., U.S. Pat. No. 4,877,611). Immunization protocolshave used adjuvants to stimulate responses for many years, and as such,adjuvants are well known to one of ordinary skill in the art. Someadjuvants affect the way in which antigens are presented. For example,the immune response is increased when protein antigens are precipitatedby alum. Emulsification of antigens also prolongs the duration ofantigen presentation. The inclusion of any adjuvant described in Vogelet al., “A Compendium of Vaccine Adjuvants and Excipients (2^(nd)Edition),” herein incorporated by reference in its entirety for allpurposes, is envisioned within the scope of this invention.

Exemplary, adjuvants include complete Freund's adjuvant (a non-specificstimulator of the immune response containing killed Mycobacteriumtuberculosis), incomplete Freund's adjuvants and aluminum hydroxideadjuvant. Other adjuvants comprise GMCSP, BCG, aluminum hydroxide, MDPcompounds, such as thur-MDP and nor-MDP, CGP (MTP-PE), lipid A, andmonophosphoryl lipid A (MPL). RIBI, which contains three componentsextracted from bacteria, MPL, trehalose dimycolate (TDM) and cell wallskeleton (CWS) in a 2% squalene/Tween 80 emulsion also is contemplated.MF-59, Novasomes®, MHC antigens may also be used.

The VLPs of the invention can also be formulated with “immunestimulators.” The term “immune stimulator” refers to a compound thatenhances an immune response via the body's own chemical messengers(cytokines). These molecules comprise various cytokines, lymphokines andchemokines with immunostimulatory, immunopotentiating, andpro-inflammatory activities, such as interleukins (e.g., IL-1, IL-2,IL-3, IL-4, IL-12, IL-13); growth factors (e.g., granulocyte-macrophage(GM)-colony stimulating factor (CSF)); and other immunostimulatorymolecules, such as macrophage inflammatory factor, Flt3 ligand, B7.1;B7.2, etc. The immune stimulator molecules can be administered in thesame formulation as VLPs of the invention, or can be administeredseparately. Either the protein or an expression vector encoding theprotein can be administered to produce an immunostimulatory effect. Thusin one embodiment, the invention comprises antigenic and vaccineformulations comprising an adjuvant and/or an immune stimulator.

Methods of Stimulating an Immune Response

The VLPs of the invention are useful for preparing compositions thatstimulate an immune response that confers immunity or substantialimmunity to infectious agents. Both mucosal and cellular immunity maycontribute to immunity to infectious agents and disease. Antibodiessecreted locally in the upper respiratory tract are a major factor inresistance to natural infection. Secretory immunoglobulin A (sIgA) isinvolved in protection of the upper respiratory tract and serum IgG inprotection of the lower respiratory tract. Protection of the respiratorytract is important in the case of influenza and other infections thatare transmissible through the respiratory system. The immune responseinduced by an infection protects against reinfection with the same virusor an antigenically similar viral strain.

VLPs of the invention can stimulate the production of antibodies that,for example, neutralize infectious agents, block infectious agents fromentering cells, block replication of said infectious agents, and/orprotect host cells from infection and destruction resulting in a“protective immune response”. A protective immune response can alsorefer to an immune response that is mediated by T-lymphocytes and/orother white blood cells against an infectious agent, exhibited by avertebrate (e.g., a human), that prevents or ameliorates infection (e.g.influenza infection) or reduces at least one symptom thereof.

Recently there has been a concerted effort to create a vaccine againstavian influenza virus that has the potential to create a pandemic. Thatis because a number of avian influenza viruses have crossed the speciesbarrier and directly infected humans resulting in illness and, in somecases, death. These viruses were H5N1, H9N2 and H7N7 (Cox et al., 2004).A recent study examined the potential of using inactivated H5N1influenza virus as a vaccine. The formulation of the vaccine was similarto the licensed inactivated vaccines currently licensed for marketing.The study concluded that using inactivated H5N1 virus did induce animmune response in humans, however the dose given was very high (90 μgof avian influenza compared to 15 μg of the licensed vaccine) (Treanoret al., 2006). This high amount of avian influenza antigen isimpractical for a worldwide vaccination campaign. The VLPs of theinvention can induce an immune response in a vertebrate whenadministered to said vertebrate, and may be more efficient in inducingimmunity than inactivated virus.

In addition to the trepidation of infection with potentially pandemicavian influenza viruses, frequent mutations in influenza viral antigensthat create new variants or viral strains is problematic when attemptingto develop vaccines to protect the public from influenza infection. Oneapproach to solve this problem is to administer seasonal influenzavaccines to humans every year to reduce the incidence of influenzacases. At present, there are two subtypes of influenza A and influenza Bcirculating in the United States. Current vaccines are, therefore,trivalent to provide protection against the strains currentlycirculating. Each year a different strain or variation of an influenzavirus changes. Thus, for most years a new vaccine composition ismanufactured and administered. Inactivated vaccines are produced bypropagation of the virus in embryonated hens' eggs. The allantoic fluidis harvested, and the virus is concentrated and purified, theninactivated. Thus, the current licensed influenza virus vaccines maycontain trace amounts of residual egg proteins and, therefore, shouldnot be administered to persons who have anaphylactic hypersensitivity toeggs. In addition, supplies of eggs must be organized and strains forvaccine production must be selected months in advance of the nextinfluenza season, thus limiting the flexibility of this approach andoften resulting in delays and shortages in production and distribution.In addition, some influenza strains do not replicate well in embryonatedchicken eggs which may limit the influenza strains which can be grownand formulated into vaccines. VLPs of the invention do not require eggsfor production, as they are made via a cell culture system. This featureof the VLPs combined with the ease with which the VLPs can be made tocontain emerging variants of the influenza antigenic proteins couldpotentially make influenza vaccine production more efficient andaccessible to a greater portion of the population.

Thus, the invention encompasses a method of inducing protective immunityto an infection in a subject, comprising administering to the subject anantigenic formulation or vaccine comprising VLPs, wherein said VLPscomprise at least one chimeric protein, but does not include aninfluenza matrix (M1) protein. In one embodiment, said VLPs furthercomprise at least one additional protein from an infectious agent. Inanother embodiment, said chimeric protein contains the cytoplasmic tailof an influenza membrane protein. In another embodiment, said influenzamembrane protein is HA, NA, or M2. In another embodiment, said chimericprotein contains the transmembrane domain of an influenza membraneprotein. In another embodiment, said influenza membrane protein is HA.In another embodiment, said VLPs do not contain a viral matrix or coreprotein. The chimeric proteins may contain the extracellular domains ofantigenic proteins, such as HA and NA, from different viral strains thanthat from which the cytoplasmic tail or transmembrane domains arederived. For illustration purposes, one possible chimeric protein of theinvention could contain the extracellular domain from a HA protein froman avian influenza virus (e.g. H5) fused to a cytoplasmic tail from a HAprotein from a seasonal influenza virus. VLPs comprising multiplechimeric proteins, wherein the chimeric proteins contain extracellulardomains from different antigenic proteins (e.g. H5 in first chimericprotein and a HA protein variant from a seasonal influenza virus insecond chimeric protein) are also contemplated within the scope of theinvention. These VLPs containing different combinations of chimericproteins could be used to produce a vaccine directed to several types ofinfluenza virus.

Another embodiment of the invention comprises a method of inducingprotective immunity to an infection in a subject, comprisingadministering to the subject an antigenic formulation or vaccinecomprising VLPs, wherein said VLPs comprise at least one influenzamembrane protein, but do not contain an influenza matrix (M1) protein.In one embodiment, said VLPs further comprise at least one additionalprotein from an infectious agent. In another embodiment, said influenzamembrane protein is HA. In another embodiment, said HA protein is aseasonal or avian HA. In another embodiment, said VLPs further comprisea NA protein. In another embodiment, said HA and NA are H5N1. In anotherembodiment, said VLPs do not contain a viral matrix or core protein.

As mentioned above, the VLPs of the invention prevent or reduce at leastone symptom of influenza infection in a subject. Symptoms of influenzaare well known in the art. They include fever, myalgia, headache, severemalaise, nonproductive cough, sore throat, weight loss and rhinitis.Thus, the method of the invention comprises the prevention or reductionof at least one symptom associated with influenza viral infection. Areduction in a symptom may be determined subjectively or objectively,e.g., self assessment by a subject, by a clinician's assessment or byconducting an appropriate assay or measurement (e.g. body temperature),including, e.g., a quality of life assessment, a slowed progression ofan influenza infection or additional symptoms, a reduced severity of ainfluenza symptoms or a suitable assays (e.g. antibody titer and/orT-cell activation assay). The objective assessment comprises both animaland human assessments.

This invention is further illustrated by the following examples thatshould not be construed as limiting. The contents of all references,patents and published patent applications cited throughout thisapplication, as well as the Figures, are incorporated herein byreference for all purposes.

EXAMPLES Example 1 VLP Formation Induced by Expression of Influenza HAand NA Proteins

Influenza A/Sydney/5/97 (H3N2) virus HA, NA M1, M2, and NP genes wereexpressed in Spodoptera frugiperda cells (Sf-9S cell line; ATCCPTA-4047) using the baculovirus bacmid expression system. Infection ofpermissive Sf-9S insect cells with recombinant baculovirus resulted inco-expression of all five influenza genes or subcombinations thereof ineach Sf-9S cell infected with such recombinant baculovirus. The samples,as defined below, are the influenza proteins expressed in a single cellor controls. HPV 16L1, a protein from human papilloma virus, is used asa control.

Samples: 1. HA+NA+NP+M1+M2 2. HA+NA+NP+M1+M2

3. wt baculovirus

4. HA+NA

5. uninfected Sf9 cells

6. HPV 16L1

After growing the infected cells for four days, the cells were pelletedand frozen at −80° C. The cells were thawed at room temperature,resuspended in 4 ml of PBS, pH6.8 and transferred into 560 ml tubes. Thecells were sonicated and clarified via centrifugation. Next, Sorvall 12ml tubes filled with 1 ml of 60% sucrose/PBS, 4 ml of 20% sucrose/PBS pH6.8 and the clarified cell suspension were placed into a centrifuge tubeand centrifuged for 3 hr @28000 rpm. The fractions were taken asdepicted in FIG. 1. Approximately 1 ml fractions were collected.Fractions collected at the 20%/60% sucrose interface (fraction 3)typically contain virus-like particles if they are present in thesample. In addition, supernatants of the growth media were saved (aftercentrifugation) for further analysis.

Fractions taken from the 20%/60% sucrose interface (fraction 3 inFIG. 1) from the different samples listed above were analyzed by westernblot analysis (FIG. 2). Blots of samples taken 2 days (top blot) or 3days (bottom blot) post-infection were probed with serum against H3N2influenza virus. Several immunoreactive bands are observed on the blotsindicating the presence of influenza viral proteins in virus-likeparticles. The strongest band represents the immunodominant HA influenzaprotein. Fractions taken from sample 4 (HA+NA) exhibit immunoreactivebands on these blots (lane 5), indicating VLP formation in cellsexpressing only HA and NA influenza proteins.

Samples defined above were also analyzed by high performance liquidchromatography (HPLC). FIG. 3 shows traces obtained from these samplesas well as traces from two influenza virus samples. Fractions obtainedfrom cells expressing only influenza HA and NA proteins show a similarchromatographic profile to that of Influenza samples 1 and 2. These dataalso suggest that VLP formation occurs when the HA and NA proteins areexpressed without M1.

A second experiment similar to the one described above was conductedexcept that after samples were purified through the sucrose gradient,fractions were further purified through a second sucrose gradient. Inthis experiment, a 1 ml fraction was collected at the 20%/60% sucroseinterface and subjected to a linear sucrose gradient from 20% to 60%(FIG. 4). This gradient was centrifuged for 16 hours @28,000 rpm. Thefractions were collected as indicated in the figure. The samples, asdefined below, are the influenza proteins expressed in a single cell orcontrols.

Samples (Cell Lysates): 1. HA+NA+NP+M1+M2 2. HA+NA 3. HPV 16L1

4. Influenza A purified virionsThe cell lysates were processed as described above.

Cell lysates from sample #2 described above (HA+NA) were processedthrough the procedure shown in FIG. 4. Fractions collected from thesecond sucrose gradient were subjected to Western blot analysis (FIG.5). The blot was probed with serum against H3N2 influenza virus. Lanes3-14 contain fractions 0-11 collected from the second sucrose gradient.Immunoreactive bands are evident in lanes 5 to 11 suggesting thepresence of VLPs in the sample. Note the strongest band (lane 6)correlates to the fraction of the sucrose gradient (30%) where one wouldexpect the majority of VLPs to be located.

Samples described above (HA+NA, HPV 16L1, and influenza purifiedvirions) were separated by HPLC (FIG. 6). The sample HA+NA#3 has a largepeak at about the same size as the control flu VLP#3. These data areindicative of VLP formation in cells expressing HA and NA only.

Example 2 Expression of Single Influenza Membrane Proteins Induces VLPFormation

Sf9 cells were infected with recombinant baculovirus expressing variousinfluenza proteins or combinations thereof. Infected cells wereincubated in serum-free medium. The media supernatants were pelletedthrough 20% sucrose cushion. Pellets were resuspended and subjected towestern blot analysis. The blot was probed using a polyclonal antibodyspecific for influenza virus (FIG. 7).

Lanes:

1. Molecular weight standard

2. HA+NA+NP+M1+M2 3. HA+NA+M1+M2 4. HA 5. NA 6. M1 7. M2

Immunoreactive bands are observed in all lanes, but lane 7. These datashow that influenza proteins are present in the material, likely VLPs,which could be purified by pelleting through sucrose cushion. Therefore,the supernatant from cells infected with baculovirus expressing eitherHA protein only, NA protein only or M1 protein only exhibited evidenceof VLP formation.

Example 3 Expression of Chimeric Proteins Derived from InfluenzaMembrane Proteins Drives VLP Formation

Sf9 cells were infected with recombinant baculovirus expressing chimericproteins. The chimeric proteins contained enhanced green fluorescentprotein (eGFP) fused to either the cytoplasmic tail of influenza M2protein or the cytoplasmic tail of influenza HA protein as illustratedin FIG. 8. Supernatants of the infected cells were purified through asucrose gradient and subjected to SDS-PAGE and western blot analyses.The resulting coomassie-stained gel is shown in FIG. 9A and thecorresponding western blot is shown in FIG. 19B. The blot in FIG. 9B wasprobed with a polyclonal antibody against GFP. The immunoreactive bandspresent in lanes 2 and 4 indicate the presence of chimeric proteins(eGFP-M2 cytoplasmic tail and eGFP-HA cytoplasmic tail, respectively) inthe supernatant samples purified by sucrose gradient. These data suggestthat VLPs are formed in cells expressing the chimeric proteins.

In another experiment, a second type of chimeric protein wasconstructed, which contained the transmembrane domain of influenza HAprotein fused to glycoprotein E (gE) of Varicella Zoster virus (VZV).Example sequences is illustrated below.

Seq Id. 4 VZV gE fused to the transmembrane domain of HA (underlined)MGTVNKPVVG VLMGFGIITG TLRITNPVRA SVLRYDDFHT DEDKLDTNSV YEPYYHSDHAESSWVNRGES SRKAYDHNSP YIWPRNDYDG FLENAHEHHG VYNQGRGIDS GERLMQPTQMSAQEDLGDDT GIHVIPTLNG DDRHKIVNVD QRQYGDVFKG DLNPKPQGQR LIEVSVEENHPFTLRAPIQR IYGVRYTETW SFLPSLTCTG DAAPAIQHIC LKHTTCFQDV VVDVDCAENTKEDQLAEISY RFQGKKEADQ PWIVVNTSTL FDELELDPPE IEPGVLKVLR TEKQYLGVYIWNMRGSDGTS TYATFLVTWK GDEKTRNPTP AVTPQPRGAE FHMWNYHSHV FSVGDTFSLAMHLQYKIHEA PFDLLLEWLY VPIDPTCQPM RLYSTCLYHP NAPQCLSHMN SGCTFTSPHLAQRVASTVYQ NCEHADNYTA YCLGISHMEP SFGLILHDGG TTLKFVDTPE SLSGLYVFVVYFNGHVEAVA YTVVSTVDHF VNAIEERGFP PTAGQPPATT KPKEITPVNPGTSPLLRQIL SIYSTVASSL ALAIMMAGLS LWMCSNGSLQ CRICI

Sf9 cells were infected with recombinant baculovirus expressing the VZVgE-HA transmembrane chimeric protein. Cell lysates from infected cellswere purified through a 20%-60% sucrose density gradient and variousfractions collected. Fractions in which VLPs are expected to equilibrate(30% sucrose fraction) were run on an SDS-PAGE gel (FIG. 10A) andsubsequently analyzed by western blot. Blots were probed with anantibody against VZV glycoprotein E (FIG. 10B) or an antibody againstinfluenza M1 protein (FIG. 10C). The appearance of bands in lanes 1 and2 of FIG. 10B indicate the formation of VLPs in cells expressing thechimeric protein containing the transmembrane domain of influenza HAprotein fused to gE of VZV.

All patents, publications and patent applications herein areincorporated by reference to the same extent as if each individualpatent, publication or cited patent application was specifically andindividually indicated to be incorporated by reference.

The foregoing detailed description has been given for clearness ofunderstanding only and no unnecessary limitations should be understoodtherefrom as modifications will be obvious to those skilled in the art.It is not an admission that any of the information provided herein isprior art or relevant to the presently claimed inventions, or that anypublication specifically or implicitly referenced is prior art.

Unless defined otherwise, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which this invention belongs.

While the invention has been described in connection with specificembodiments thereof, it will be understood that it is capable of furthermodifications and this application is intended to cover any variations,uses, or adaptations of the invention following, in general, theprinciples of the invention and including such departures from thepresent disclosure as come within known or customary practice within theart to which the invention pertains and as may be applied to theessential features hereinbefore set forth and as follows in the scope ofthe appended claims.

1. A purified VLP comprising at least one chimeric influenza membraneprotein, wherein the VLP does not contain an influenza matrix (M1)protein.
 2. The VLP of claim 1, wherein the VLP further comprises atleast one additional protein from an infectious agent.
 3. The VLP ofclaim 1, wherein said chimeric protein comprises the cytoplasmic tail ofan influenza membrane protein.
 4. The VLP of claim 3, wherein saidinfluenza membrane protein is selected from the group consisting of HA,NA, and M2.
 5. The VLP of claim 1, wherein said chimeric proteincomprises the transmembrane domain of an influenza membrane protein. 6.The VLP of claim 5, wherein said influenza membrane protein is HA. 7.The VLP of claim 1, wherein the VLP does not contain a viral matrix orcore protein.
 8. A purified VLP comprising at least one influenzamembrane protein, wherein the VLP does not contain an influenza matrix(M1) protein.
 9. The VLP of claim 8, wherein the VLP further comprisesat least one additional protein from an infectious agent.
 10. The VLP ofclaim 9, wherein said influenza membrane protein is HA.
 11. The VLP ofclaim 10, wherein the HA is a seasonal or avian HA.
 12. The VLP of claim10, wherein the VLP further comprises an influenza NA protein.
 13. TheVLP of claim 12, wherein the HA and NA are H5N1.
 14. The VLP of claim 8,wherein the VLP does not contain a viral matrix or core protein.
 15. Amethod of making a VLP, comprising: expressing at least one chimericinfluenza membrane protein in a cell; and purifying the VLPs, whereinthe cell does not express an influenza matrix (M1) protein.
 16. Themethod of claim 15, wherein said chimeric protein comprises thecytoplasmic tail of an influenza membrane protein.
 17. The method ofclaim 16, wherein said influenza membrane protein is selected from thegroup consisting of HA, NA, and M2.
 18. The method of claim 15, whereinsaid chimeric protein comprises the transmembrane domain of an influenzamembrane protein.
 19. The method of claim 18, wherein said influenzamembrane protein is HA.
 20. The method of claim 15, wherein the celldoes not contain a viral matrix or core protein.
 21. The method of claim15, further comprising expressing at least one additional protein froman infectious agent in said cell.
 22. A method of making a VLP,comprising: expressing at least one influenza membrane protein in acell; and purifying the VLPs, wherein the cell does not express aninfluenza matrix (M1) protein.
 23. The method of claim 22, furthercomprising expressing at least one additional protein from an infectiousagent in said cell.
 24. The method of claim 23, wherein said influenzamembrane protein is HA.
 25. The method of claim 24, wherein the cellfurther expresses an influenza NA protein.
 26. The method of claim 22,wherein the cell does not contain a viral matrix or core protein.
 27. Avaccine comprising a VLP, wherein said VLP comprises a chimericinfluenza membrane protein, but does not contain an influenza matrix(M1) protein.
 28. The vaccine of claim 27, wherein said chimeric proteinincludes the cytoplasmic tail of an influenza membrane protein.
 29. Thevaccine of claim 28, wherein said influenza membrane protein is selectedfrom the group consisting of HA, NA, and M2.
 30. The vaccine of claim27, wherein said VLP further comprises at least one additional proteinfrom an infectious agent.
 31. The vaccine of claim 27, wherein saidchimeric protein includes the transmembrane domain of an influenzamembrane protein.
 32. The vaccine of claim 31, wherein said influenzamembrane protein is HA.
 33. An vaccine comprising a VLP, wherein saidVLP comprises an influenza membrane protein, but does not contain aninfluenza matrix (M1) protein.
 34. The vaccine of claim 33, wherein saidVLP further comprises at least one additional protein from an infectiousagent.
 35. The vaccine of claim 34, wherein said influenza membraneprotein is HA.
 36. The vaccine of claim 35, wherein said HA is seasonalor avian HA.
 37. The vaccine of claim 35, wherein said VLP furthercomprises an influenza NA protein.
 38. The vaccine of claim 35, whereinsaid HA is from influenza virus H3N2.
 39. The vaccine of claim 37,wherein said HA and NA are H5N1.
 40. An antigenic formulation comprisinga VLP, wherein said VLP comprises a chimeric protein, but does notcontain an influenza matrix (M1) protein.
 41. The antigenic formulationof claim 40, wherein said chimeric protein includes the cytoplasmic tailof an influenza membrane protein.
 42. The antigenic formulation of claim41, wherein said influenza membrane protein is selected from the groupconsisting of HA, NA, and M2.
 43. The antigenic formulation of claim 40,wherein said VLP further comprises at least one additional protein froman infectious agent.
 44. The antigenic formulation of claim 40, whereinsaid chimeric protein includes the transmembrane domain of an influenzamembrane protein.
 45. The antigenic formulation of claim 44, whereinsaid influenza membrane protein is HA.
 46. An antigenic formulationcomprising a VLP, wherein said VLP comprises an influenza membraneprotein, but does not contain an influenza matrix (M1) protein.
 47. Theantigenic formulation of claim 46, wherein said VLP further comprises atleast one additional protein from an infectious agent.
 48. The antigenicformulation of claim 47, wherein said influenza membrane protein is HA.49. The antigenic formulation of claim 48, wherein said HA is seasonalor avian HA.
 50. The antigenic formulation of claim 48, wherein said VLPfurther comprises an influenza NA protein.
 51. The antigenic formulationof claim 50, where said HA and NA are H5N1.
 52. A method of inducingprotective immunity to an infection, comprising administering a vaccineof claim 27 to a subject.